The present invention relates generally to digital data transmission and more specifically to transmission of data at different rates over a fixed rate transmission system.
A number of high-speed digital interface standards exist that support variable data rates. The term variable data rate references the fact that the standard does not fix a specific rate for data transmission. Other digital interface standards, limit the rates at which data can be transmitted between a number of fixed rates. Due to the fact the data rate is unknown to the receiver in such digital interface standards, a clock signal is typically provided to enable synchronization between the transmitter and receiver. Therefore, a device utilizing a digital interface standard, where the data rate is unknown to the receiver, typically transmits data at a fixed rate indicated by a clock signal provided by the device. A receiver can then be configured to receive the data at the rate indicated by the clock signal. Examples of variable data rate digital interface standards include the High Definition Multimedia Interface (HDMI) promoted by HDMI Licensing, LLC of Sunnyvale Calif. and the Digital Visual Interface (DVI) standard developed by the Digital Display Working Group of Vancouver, Wash. Examples of digital interface standards that specify a number of allowed data rates include the Display Port standard issued by the Video Electronics Standards Association of Milpitas, Calif.
Signal attenuation limits the length of cable over which a signal can be transmitted. In many instances, an optic fiber link can be used to increase the distance over which data can be transmitted. The transmission of variable rate data using a fixed rate transmission system, such as a transmission system including an optic fiber link, can be problematic. A clock signal matched to the rate of the data is required for a receiver to receive variable rate data and fixed rate systems typically do not provide support for transmission of the clock signal.